What is a bilateral aid agency?
a. an agency that receives funding from two donors
b. an agency that focuses on two main health problems
c. development assistance agencies of high income countries
d. development assistance agencies of low income countries

In an experiment examining the effects tai chi on arthritis pain, callahan (2010) selected a large sample of individuals with doctor-diagnosed arthritis. half of the participants immediately began a tai chi course and the other half (the control group) waited 8 weeks before beginning. at the end of 8 weeks, the individuals who had experienced tai chi had less arthritis pain that those who had not participated in the course.